How to analyze curious ping issue?

[Asperamanca]

I have a wireless (Phone) and a wired device (PC) in the same VLAN.
Since they get correct IP addresses in the same subnet, I conclude that
a) they can both reach the Firewall
b) they are connected via the same interface (and thus to the same VLAN)

From the firewall I can ping both devices.

However, the PC cannot ping the phone ("destination host cannot be reached")
If I connect the PC via wireless as well, I can ping the phone.

How can I analyze this issue?

[bartjsmit]

Compare the settings on the two DHCP servers:

- do their ranges overlap?
- do they issue the same subnet mask?

Are you pinging by IP address or by name?

Make sure the WiFi AP does not NAT.

If possible, set the WiFi in AP-only mode and use a single DHCP server.

Bart...

[Asperamanca]

Thank you for your input!

The firewall is the DHCP server for both. DHCP is disabled on the Wifi AP, and the IP addresses used are consistent with the DHCP settings on the firewall.
I am pinging by IP address.
I have set up the Wifi-AP from scratch, and have not configured any NAT rules.

I have since found that I can ping the phone from a different wired PC (Windows 10). But even disabling the Windows Firewall on the original PC doesn't change anything.

Further suggestions on what to try?

EDIT: Small update: Now I cannot reach my phone from PC 1 even if I am connected to the same Wifi. I thought I had a workaround there...

[chemlud]

I don't really see where OPNsense comes into play. Ping by IP on the same LAN should not reach the router, but only the switch the PC and the wifi-AP are connected to. Did you try without VLAN?

You could use Wireshark in promiscous mode to see which packages are going back and forth on your LAN...

[Asperamanca]

I don't really see where OPNsense comes into play.

Which is why I posted to the "General" section.
Anyway, I gave the Wifi AP a static IP address in the OPNsense DHCP configuration, and now I can ping my wireless devices. At least for the moment...